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International Journal of Advanced Technology & Engineering Research (IJATER)www.ijater.com tan 1 ( )2 0.25a 1( ) cos 2L2b a tan2 tan 2 22cotha1 cot b cotb1 coth a12 cot b 1coth acoth a 1cot2b 20.52 0.25221 cotha cot b3C-SiC 800 300 207.2 77.7The variation of total resistance of p-i-n diode with frequency(0.1MHz – 30GHz) for three different semiconductors (3C-SiC,GaAs,Si) are shown in fig2 – fig4.In each case has beencalculated at 1mA forward biased current consideringW=0.12mils and Q=8.4C………………………………… (5)Figure1. The p-i-n diode, showing i- region and the junctionregionsNow in the p-i-n diode the normalized resistance can be definedasR 2R( f )TRj 1 ………………………………… (6)iRiFigure2. Total resistance of 3C-SiC p-i-n diode at 1mAforward current versus frequency.Based on equations (1)-(6) the resistance of p-i-n diode has beenestimated considering the forward bias current as 1 mA. Theanalysis of resistance in p-i-n diode has been carried out usingSi, GaAs and 3C-SiC as semiconductor material and thecalculated resistances at higher frequencies using these threedifferent materials are compared. The p-i-n diode resistancedepends on i- region characteristics and geometry which havebeen analyzed using different W/L ratio.TABLE I: Parameters of different semiconductorMaterialMobility ofElectrons(µ n)cm 2sMobilityofHoles(µ p)cm 2sDiffusionconstant ofElectrons(D n)2cmv sDiffusionconstant ofHoles(D p )2cmv sSi 1350 12.4 25 480GaAs 8500 400 220 10.4Figure3. Total resistance of Ga-As p-i-n diode at 1mAforward current versus frequency.ISSN No: 2250-3536 Volume 3, Issue 1, Jan. 2013 20
International Journal of Advanced Technology & Engineering Research (IJATER)www.ijater.com3. Result and AnalysisThe p-i-n switch shows that irrespective of base material it canoffer better switching action. In SiC the off resistance is highercompare to GaAs and Si where as the band gap energy, meltingtemperature and other properties of SiC are more suitable for itsapplication as SPST switch at higher frequency (~30 GHz ormore). The normalized resistance of switch shows that (W/L)ratio has an important contribution to control the resistancecharacteristics. This is also evident from equation (6). With thediffusion length increase the resistance become low but thetransition of switch is not sharp compare to higher value of(W/L).This p-i-n diode can be used at higher frequency (~35 GHz) asSPST switch in Radar, Missile technology where number ofIMPATT diodes are connected and the SPST switch controlsthem.Figure4. Total resistance of Si p-i-n diode at 1mA forwardcurrent versus frequency.Figure5. The normalized resistance for 3C-SiC p-i-n diodeversus frequency-lifetime product fτ.Among these three materials SiC is WBG semiconductors andoffers better applications at microwave frequencies [7,8,9] thusthe normalized resistance of p-i-n diode has been calculated forSiC material only. The variation of normalized resistance as afunction of fτ is shown in fig.5 for different values of W/L.4. REFERENCES[1] Caverly,R.,Hiller, G., “Microwave resistance ofGallium Arsenide and Silicon p-i-n Diode”, IEEEMTT-S Digest,1987[2] A. Iturri-Hinojosa, L.M Resendize, and T.VTorchynska, “Numerical Analysis of the Performanceof p-i-n Diode Microwave Switches Based onDifferent Semiconductor Materials”,Int.J.pureAppl.sci,Technology,2010.[3] Emmanull Gated, et.al., “An improved physics- BasedFormulation of the Microwave p-i-n diodeimpedance”, IEEE microwave and Wirelesscomponents Letters, Vol.17. No.3, March 2007.[4] D.Leenov, “The Silicon p-i-n dode as a microwaverader protector at megawatt levels”, IEEE Trans.Electron Devices, Vol. ED-11, no.2, PP.53-61, Feb.1964.[5] R.H. Caverly and G. Hiller “The small signal acimpedance of gallium arsenide and silicon p-i-ndiode”, solid state electron, Vol.33, no.10, PP.1255-1263,1990.[6] Size, S.M., “Physics of Semiconductor Devices”, JhonWilly and Sons, New York, 1989.[7] M.Ray Kanjilal, D.Ghosh, M. Mukherjee, “Studies ofElectrical Characteristics of MESFET Using WBG IV-IV SiC AS Potential Substrate Material”, IJSAT, Vol2 no 6, PP. 71 – 76, June 2012.ISSN No: 2250-3536 Volume 3, Issue 1, Jan. 2013 21
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